In the past, an exhaust pipe for a vehicle, such as a flexible pipe as shown in FIG. 8, is well known. That is, the flexible pipe 1 is a component capable of preventing the vibration from an engine side from being transferred to a downstream member. An interlocking-type flexible pipe 2 (hereinafter referred to as “interlocking pipe”) for connecting an upstream member and the downstream member is arranged in the middle. Bellow 3 and an outer plate 4 are arranged outside the interlocking pipe. An end 3a of the bellow 3 and an end 4b of the outer plate 4 are provided with a protection element 5 bent in such a manner as to coincide with two ends of the interlocking pipe 2.
However, for the interlocking pipe 2 of the flexible pipe 1, as shown by the arrow in FIG. 8, a tabular metal band plate 2a is shaped into a curved metal band plate 2b (see FIG. 9) with an S-shaped cross section and wound helically so that bending portions at both sides thereof are engaged with each other. As a result, it is able to form the flexible interlocking pipe which can be stretched in both axial and radial directions.
Moreover, when shaping the interlocking pipe, the elongate tabular metal band plate 2a with a certain width is extracted from a decoiler 6 as shown in FIG. 9. The band plate 2a is coated with lubricating oil by an oil-applying device 7 while entering a multistage roll-forming device 8, and passes through a space between an upper roller 8a and a lower roller 8b, so as to form tabular metal band plate 2a into the curved metal band plate 2b with an S-shaped cross section (as shown by an extended line in FIG. 8). This curved metal band plate 2b is fed into a winding device 9 and helically wound in a way that the sides thereof are engaged with each other. Finally, it is cut into a predetermined length by a plasma cutting device (not shown).
In addition, the interlocking pipe 2 has a cross section with a circular shape or a polygonal shape. For example, Patent Literature 1 discloses that, for an interlocking pipe with a circular cross section, although with excellent impermeability, it is rotatable and thus easy to loosen, i.e., it has defects of being loosened and easy to be detached; while for an interlocking pipe with a polygonal cross section, although with poor impermeability, it is able to accurately set the rigidity of the interlocking pipe and the detachability of a guiding portion connected thereto due to the vibration. The polygonal end enables the hose to rotate without loosening while maintaining its predetermined shape and winding state (see paragraphs [0002]-[0005] of the Patent Literature).
That is, for the interlocking pipe with a polygonal cross section, although a core member with a polygonal cross section is used during winding, it can be hung over a polygonal end of the core member. Patent Literature 2 (see FIG. 2) and Patent Literature 4 (see FIG. 12) show such an interlocking pipe with a polygonal cross section.
On the other hand, for the interlocking pipe with a circular cross section, although a core member with a circular cross section is used during winding, it cannot be hung over due to its circular shape, and springback will occur during the winding, the pipe cannot be wound while maintaining its predetermined shape. In addition, rotation and loose may occur due to the springback of the thrust.
In order to overcome the above-mentioned drawbacks, Patent Literature 4 discloses in FIG. 1 that, after the interlocking pipe is wound into a diameter less than that of the final shape, a rewinding force, or a force in a direction opposite to a rotation direction, is applied to the interlocking pipe. The force in a direction opposite to the rotation direction may be applied by a roller or an elastic member.